(a) Field of the Invention
The present invention relates to organic optical logic devices, particularly to organic optical logic devices which are useful in various fields, including optical information processing, optical communication, optoelectronics and laser application fields.
(b) Description of the Related Art
The importance of nonlinear optical materials is increasing with the recent advance of optical communication optoelectronics. The development of highly efficient optical logic devices utilizing nonlinear optical effects is essential to the future applications of high-speed optical switches or optical computers, and such a development requires highly efficient nonlinear optical materials and devices utilizing them.
Heretofore, some optical logic devices have been proposed. They are produced mainly by using semiconductors, particularly GaAs or GaAlAs. These materials have strong optically nonlinear properties attributable to the real excitation of excitons, thereby forwarding the developments of practical devices and systems. The response time of the devices made of these materials, however, depends on the recombination times of excitons, so that it is impossible to shorten the response time below nanoseconds. Further, the production of such devices needs large cost and a great deal of labor because of the complicated structures thereof and the necessity for treating raw materials of high purity in ultra high vacuum circumstances. As to the problem of the response time, the response time can be improved by applying voltage to devices so that the generated excitons are separated into free carriers and are removed from the devices rapidly. Even in this case, it is difficult to reduce the response time to 100 ps or less since it is dominated by the mobility of electrons and positive holes, and other problems including a great increase of the consumption energy arise. Therefore, various kinds of devices have been made by way of trial but have not yet received practical application.
In order to overcome these problems, there have been devised optical devices that utilize polaritons of semiconductors (Japanese Patent Application Kokai Koho (Laid-open) No. 63-110414, Japanese Patent Application Kokai Koho (Laid-open) No. 63-197915). These devices utilize the nonlinear optical absorption effects of polaritons of CuCl or GaAs, and the reported response time is one ps, which is improved as compared with that of the conventional devices. These devices however have a shortcoming of exhibiting the good performance only at cryogenic temperatures around 4.degree. K.
There have also been made researches of various kinds of organic materials. For example, in Example 2 of Japanese Patent Application Kokai Koho (Laid-open) No. 2-183229 is disclosed an organic material having a third order nonlinear optical coefficient .gamma.=8.5.times.10.sup.-28 (esu). An assumption of the nonlinear optical coefficient of the crystal of the organic material in consideration of the molecular concentration provides a value of 5.times.10.sup.-7 (esu). The response time however is not reported. The value of the third order nonlinear optical coefficient is so fairly larger than those of former materials that the material is applicable for specific uses, such as electrooptic modulators, but is still insufficient for applications in general purpose optical switches or optical computer devices.